This invention relates to a fuel injection system associated with multicylinder internal combustion engines. The system includes a fuel injection pump, from the pump work chamber of which a "main" or "larger" fuel quantity is delivered through a pressure conduit (main conduit) to at least one cylinder of said engine. From said pressure conduit there extends an auxiliary conduit for simultaneously supplying an "ignition" or "smaller" fuel quantity to at least one other cylinder. The two named cylinders operate out of phase due to the angularly offset cranks of the crankshaft.
In fuel injection systems of this type the fuel to be combusted is injected into at least one cylinder in two parts, resulting in a particularly good combustion.
According to a known fuel injection system of the aforenoted type (disclosed, for example, in U.S. Pat. No. 3,216,407), the auxiliary conduit merges into the main conduit of a cylinder operating with a phase shift of half a work cycle. According to another known fuel injection system (as disclosed in German Pat. No. 1,212,782), two main conduits which lead to two cylinders operating at a phase shift of half a work cycle with respect to one another, are interconnected by an auxiliary conduit. In the auxiliary conduits of both of the aforenoted known fuel injection systems, there are disposed throttle devices to ensure that the fuel quantities flowing through the auxiliary conduit are, to a desired extent, smaller than the main fuel quantity.
The fuel injection systems outlined above have the disadvantage that a desired exact distribution of the fuel quantities, either as a constant quantity ratio or as a ratio in which one fuel quantity should remain constant, may not be obtained. The reason is that the fuel passes from one main conduit across an auxiliary conduit branch into another main conduit in which at that moment no fuel is delivered by the fuel pump, so that the liquid column contained in the last-named main conduit yields elastically. Depending upon the rpm-dependent delivery strokes (per time unit) of the fuel injection pump, this elasticity has a stronger or weaker influence, thus variably affecting the ratio of the larger and smaller fuel quantities.